Before I added the latest fix or update, and before installing Seasons, 70's, and University my plants refused to harvest even though they were at the harvest state. I now have Seasons, 70's and University and the latest updates & fixes but no mods. The only thing I have done is decorate the home and the dormitory myself - no downloaded CC other than what I purchased from the store or that I designed myself such as changing the color of furniture, walls, etc. The older plants that are in harvest (not barren) state still won't harvest. I found some new seeds and planted them and they grew without issue and a couple of them I was able to harvest from but now they too have stopped. I've tried playing with the various seasons, temperature, sunny and rain but unable to get them to harvest even though they are in harvest state. Anyone have any clue at all as to why this is happening?

Also now, my game is slowing greatly with major lags. I am guessing the last part has to do with changing colors of furniture, walls, etc.???? That is what makes it CC, correct? I do enjoy decorating!

No, the lag has nothing to do with changing designs on official objects. CC is content that was created by someone other than EA, what you have is recoloured items and these don't slow the game. See if any of this makes a difference.

For your plants, try this mod. If it doesn't work, get this one to fix them manually.